NASA's P-3 research plane begins flights this month through both clouds and smoke over the South Atlantic Ocean to understand how tiny airborne particles called aerosols change the properties of clouds and how they influence the amount of incoming sunlight the clouds reflect or absorb.

The Observations of Aerosols above Clouds and their Interactions, or ORACLES, field mission is carrying out the month-long field campaign from São Tomé and Principé, an island nation off the west coast of Africa. From there researchers will investigate an area off the coast of Angola, where two phenomena meet. One is natural: a low-lying cloud bank that naturally forms over the ocean. The other is at least partly human-made: a plume of smoke from seasonal fires set on agricultural fields across central Africa.

The short lifetime of aerosols in the atmosphere make them among the most variable components of Earth’s climate system. An umbrella term for any small particle suspended in the atmosphere, aerosols can be either light or dark, reflective or absorbent of sunlight, and can enhance or suppress the formation of cloud droplets. They can be natural, like desert dust, sea salt or pollen. They can also result from human activities, such as sulfate particles which form from the oxidation of sulfur dioxide emitted from power plants, or, as is the case in Central Africa, soot and ash from human-made fires.

“Imagine a plume of smoke,” said ORACLES Principal Investigator Jens Redemann of NASA's Ames Research Center in California's Silicon Valley. "If you see it over the contrast of a dark ocean, it looks lighter, which means the aerosols making up the smoke would have a cooling effect at the top of the atmosphere – they reflect more radiation."

Image: NASA's P-3 aircraft is prepared for departure from the Wallops Flight Facility in Virginia early in the morning Aug. 1 to support the agency's Observations of Aerosols above Clouds and their interactions or ORACLES mission. A five-year investigation, ORACLES is examining the impact aerosols from biomass burning in southern Africa has on climate as it mixes with clouds over the southeast Atlantic Ocean. The 2017 flight campaign, which runs through August, will base from São Tomé, Africa. (Credit: NASA/Patrick Black)